This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. For patients who have suffered neurotrauma due to traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH), it is of utmost importance to monitor changes in their cerebral blood flow (CBF) and oxygenation due to risk of ischemia in injured parts of the brain. In this study, we used a hybrid diffuse optical device to characterize the hemodynamic effects of head position and hyperoxia on neurotrauma patients, thereby assessing their cerebral autoregulation. The device is being developed as a portable, relatively inexpensive bedside monitor that employs non-invasive, continuous optical techniques to measure changes in CBF as well as deoxy- and oxyhemoglobin concentrations.